Abstract
Data on some production performance traits of 1000 milch Sahiwal cows from 3451 cows maintained at the Livestock Experiment Station, Bahadurnagar, Okara, Pakistan during the period from 2000 to 2009 were selected to study the relationship between 12 linear type traits and reproductive performance of the Sahiwal cows. The reproductive efficiency (RE) was measured in terms of calving interval from the first five lactations. The type scores were standardized for stage of lactation, age at first calving and scoring. The mean scores of linear type traits (rump width, stature, chest and body, suspensory ligament) varied from 72.6±0.78 to 81.1±0.83 points. The estimates of heritability (h2) for most of these type traits were medium 0.31±0.22 to high 0.82±0.31 and indicated the existence of large additive genetic variability for these traits in this breed. The phenotypic correlations of linear type traits with RE ranged between -0.1.6 ± 0.08 and 0.10 ± 0.09. All the 12 linear type traits accounted for 92.96% of the variability in RE of Sahiwal cows. Step-wise regression analysis revealed that 75% of the variation accounted by all linear type traits in RE could be predicted by a sub-set of four type traits (TT) which included stature, chest and body, pelvic angle and udder depth. It was concluded that in the case of absence of records, the reproductive performance of Sahiwal cows can be predicted at an early age using some linear type traits. Key words: Reproductive efficiency, type traits, heritability.
Highlights
Body conformation recording is not a common measurement for dairy animals in Pakistan
The scores for form traits were in medium class (70 to 80 points) except pelvic angle indicating that an average Sahiwal cow was an intermediate in height and body capacity, having well formed feet, slight set in hock for rear legs and moderate slope from hooks to pins
The scores for udder TT ranged from 72.67 to 78.95 points and revealed that the attachment of fore udder in Sahiwal cows was neither extremely tight nor broken, udder was of intermediate width, teats were centrally placed and nearly aligned and tilting inward and udder floor was at the hock
Summary
Body conformation recording is not a common measurement for dairy animals in Pakistan This is true for Sahiwal Cattle breed. Wiggans et al (2004) reported animal model estimates of heritability’s of genetic and phenotypic correlations for 15 linear TT of Ayrshire, Brown Swiss and Guernsey and 14 traits for Jersey. Several studies are available on genetic parameter estimates on conformation traits for different dairy cattle breeds in various countries. Such estimates for udder traits were reported by Rupp and Boichard (1999) for French Holsteins. The present investigation was undertaken to identify useful linear TT for prediction of RE in Sahiwal cows
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